• OPAR_StPaulMaido: 21.079°S 55.383°E 2160 m a.s.l.
• OPAR_StDenisUniv: 20.902°S 55.485°E 84 m a.s.l.
• OPAR_SteMarieAirport: 20.893°S 55.529°E 9 m a.s.l.

Observational platform

Belgium, France

• University of Reunion Island
• French National Centre for Scientific Research (CNRS)
• Royal Belgian Institute for Space Aeronomy (BIRA)

https://www.osureunion.fr/les-stations-dobservation/opar/fiche-didentite/

• Olivier Magand
  Facility PI (since 1 Jan 2025)
• Jérôme Brioude
  Facility PI (since 1 Jan 2026)
• Bart Dils (for the RTGRS component)
  PI deputy

Located in Reunion island, OPAR (Observatoire de Physique de l’Atmosphère à La Réunion) observation platform is a French facility made of 3 sites :
- OPAR-StDenisUniv : 20.902°S, 55.485°E, 70m asl (operational from 1993)
- OPAR-SteMarieAirport : 20.893°S, 55.529°E, 9m asl (operational from 1992)
- OPAR-StPaulMaido : 21.079°S, 55.383°E, 2160m asl (operational from 2012)

For the Reactive Trace Gases Remote Sensing (RTGRS) component, OPAR is recognised as a joint France-Belgium ACTRIS National Facility and Royal Belgian Institute for Space Aeronomy (BIRA) acts as the operating institute for this specific component.

Reunion island (21°S, 55°E), is a small tropical island located in the middle of the south- west Indian Ocean, affected by southeasterly trade winds near the ground, and westerlies in the free troposphere. La Réunion is far-off the main anthropogenic pollution sources and local pollution is very sparse.

The localisation of La Reunion in Southern Hemisphere subtropical area – a sparsely documented region - is strategic considering the need of atmospheric observations at a global scale. OPAR provides observations for:
- gases and particles background concentrations and properties.
- impact of biomass burning plumes on the atmospheric composition and radiative balance.
- dynamical influence of both the polar and the subtropical jet streams.
- ozone layer recovery.
- deep tropical convection, cirrus.
- composition of the tropical transition layer and troposphere-stratosphere transport at the tropics.
- boundary layer dynamics and cloud formation in a mountainous tropical insular environment.
- interdisciplinary studies: impacts of volcanic emissions on the atmosphere composition and radiative balance, role of biogenic emissions on clouds formation, impacts of marine emissions on new particles formation in a clean maritime environment.

• Baray et al. (2013). Maïdo observatory: a new high-altitude station facility at Reunion Island (21° S, 55° E) for long-term atmospheric remote sensing and in situ measurements. Atmos. Meas. Tech., 6(10), 2865-2877. https://doi.org///10.5194/amt-6-2865-2013
• Duflot et al. (2019). Preliminary results from the FARCE 2015 campaign: multidisciplinary study of the forest–gas–aerosol–cloud system on the tropical island of La Réunion. Atmos. Chem. Phys., 19(16), 10591-10618. https://doi.org/10.5194/acp-19-10591-2019
• Vigouroux et al. (2012). FTIR time-series of biomass burning products (HCN, C₂H₆, C₂H₂, CH₃OH, and HCOOH) at Reunion Island (21° S, 55° E) and comparisons with model data. Atmos. Chem. Phys., 12(21), 10367-10385. https://doi.org/10.5194/acp-12-10367-2012
• Vigouroux et al. (2009). Ground-based FTIR and MAX-DOAS observations of formaldehyde at Réunion Island and comparisons with satellite and model data. Atmos. Chem. Phys., 9(24), 9523-9544. https://doi.org/10.5194/acp-9-9523-2009
• Duflot et al. (2010). Analysis of the origin of the distribution of CO in the subtropical southern Indian Ocean in 2007. J. Geophys. Res., 115(D22). https://doi.org/10.1029/2010JD013994
• Vigouroux et al. (2018). NDACC harmonized formaldehyde time series from 21 FTIR stations covering a wide range of column abundances. Atmos. Meas. Tech., 11(9), 5049-5073. https://doi.org/10.5194/amt-11-5049-2018
• Zhou et al. (2018). Atmospheric CO and CH₄ time series and seasonal variations on Reunion Island from ground-based in situ and FTIR (NDACC and TCCON) measurements. Atmos. Chem. Phys., 18(19), 13881-13901. https://doi.org/10.5194/acp-18-13881-2018
• Zhou et al. (2016). CFC-11, CFC-12 and HCFC-22 ground-based remote sensing FTIR measurements at Réunion Island and comparisons with MIPAS/ENVISAT data. Atmos. Meas. Tech., 9(11), 5621-5636. https://doi.org/10.5194/amt-9-5621-2016